Casey Luber Seiden MS, RD

Workout Wednesday: Is afterburn legit?

Last week’s query focused on calorie “budgeting” for weight loss and how that fits in with increased hunger levels post-workout. While going to the gym for a workout is a huge boost for your metabolic health, you would be mistaken in thinking that the fridge is completely free reign for the afternoon or that becoming a couch potato for the rest of the day is a valid reward for your hard work. In other words, relying on the “afterburn” effect of your hour workout to magically erase any calories over-consumed later in the day would be an ill-advised strategy.

This week’s question dives deeper into the science of afterburn and whether or not the effects of your workout last long enough to make those late night sofa sweets matter less on leg day.

Crossfit Query: I have heard that CrossFit triggers an “after burning” effect during the day- how legitimate is that?

Calorie “budget” aside, you are already doing yourself a huge favor in terms of weight loss, by engaging in cardiovascular and strength training exercises at CrossFit. As you’re doing wall-balls, deadlifts, and kettlebell swings, remember you are increasing your muscle mass, and the more muscle mass you have, the more sensitive you are to burning calories. The “afterburn” effect you mentioned is a real phenomenon, but there are some caveats.

One study published in the journal Medicine and Science in Sports and Exercise has shown that indeed the calorie burning post-workout can continue, but only with very intense bouts of exercise, for example, 45 minutes of continuous, very high-intensity cycling that does not allow the exerciser to carry on a conversation. This could allow for an extra ~200 calories burned within the next 24 hours. However, if exercising at a moderate intensity and for a shorter duration, the after burn is essentially zilch after the first 1-2 hours when your body has started to replenish its glycogen and use less fat for energy.

Another study from the American Journal of Clinical Nutrition showed that when exercising at 50% of your VO2 max (a measurement of your body’s ability to take in oxygen and deliver to your working muscles), or rather a moderate intensity level that allows for comfortable speaking, no afterburn effect was observed.

So, where does this leave you?

Suffice it to say, that it seems that the level of intensity matters most when it comes to any added bonus of calorie burning post-workout. Top level athletes are likely continuing to burn some energy after a training session, yet they are likely least worried about calorie budgeting when performing at such high levels.

For recreational athletes looking to improve or maintain health, I feel the takeaway message as it relates to the “calories out” side of the weight loss equation is one of persistence and being mindful of your personal motivations for being in the gym. When it comes to working out, focus on your reasons for why you’re pushing your body to feel strong.

Furthermore, rather than resting on your workout laurels, remind yourself to follow through with positive choices in the kitchen, which will ultimately better aid in your calorie burning efforts for days and months to come, not only hours. Dedication and enjoyment during your sweat sessions and healthy eating ventures will produce cumulative, life-long benefits your body will thank you for in the end.